Ferrous sheet material and method of and apparatus for hardening ferrous sheet material



July 28, 1942. w; J. WALSH 2,291,361

FERROUS SHEET MATERIAL AND METHOD OF- AND APPARATUS FOR HARDENINGFERROUS SHEET MATERIAL Filed May 2, 1941 Patented July 28, 1942 FERROUSSHEET MATERIAL AND METHOD OF AND APPARATUS FOR HARDENIING FERROUS SHEETMATERIAL William J. Walsh, Chicago, 111., assignor to Inland SteelCompany, Chicago, 111., a corporation of Delaware Application May 2,1941, Serial No. 391,617

21 Claims.

My invention relates to novel ferrous sheet material and to a novelmethod of, and apparatus for, hardening ferrous sheet material ingeneral but more particularly, though not exclusively, to the hardeningof ferrous sheet material in the form of steel and of relatively lightgage, as for example of about 25 gage or lighter, to be used in themanufacture of articles requiring that the sheet material be formed toshape, as for example in the manufacture of containers, metal coated ornot, as for example by tin or terne; the sheet material requiring asurface hardening or tempering to render it sufficiently rigid or stiffto prevent fiuting and stretcher strains in forming the material toshape; this surface hardening being commonly produced by subjecting thesheet material to a skin rolling operation which, in the case of sheetmaterial to be coated with molten metal to plate it, as for example tinor terne, should effect such an amount of reduction by the skin rollingas to insure the retention in the finished coated sheet material, aftersubjection to the temperature used in the applying of the metal coatingto the sheet material, of sufficient temper to avoid fluting orstretcher strains as above referred to.

My objects generally stated are to provide improvements in the hardeningof ferrous sheet material by which the cost of producing sheets of thedesired degree of hardness or temper, may be greatly reduced; to providefor the production of sheet material having the desired degree offlatness; and other objects as will be manifest from the followingdescription.

Referring to the accompanying drawing:

Figure 1 is a view in side elevation, in the nature of a diagram, of anapparatus embodying my invention and suitable for practicing my improvedmethod and producing my novel material.

Figure 2 is a similar view showing the sheetbending means of Fig. 1, bywhich the sheet material is caused to become hardened, in open positionfor receiving the sheet material to be.

operated on.

Figure 3 is a similar, enlarged view of the sheet-bending means of Fig.l; certain portions of the apparatus shown in Fig. 4 being omitted inFigs. 1, 2 and 3 to avoid confusion.

Figure 4 is an enlarged transverse sectional view taken through thesheet-bending means, the section being taken at the line 4 on Fig. 3 andviewed in the direction of the arrow; and

Figure 5, a view like Fig. 1 of a modification 55 of the apparatus showntherein and also suitable for practicing my improved method andproducing my novel material. I

Referring to the apparatus shown in Figs. 1-4, inclusive, Ill representsa single passskin mill shown as of the well known 4-high roll type thework rolls of which, shown at II, are backed by relatively large backingrolls I2.

Shown as located in advance of the skin mill II] are means I3 forbending the sheet material I4 to be operated on to produce hardening andflattening of the material, which may be supplied in coil form to theapparatus, any suitable means for rotatably supporting the coil topermit it to unwind therefrom being provided.

The means I3 in the form shown, comprise a pair of parallel idler rollsI5 and I6 either smooth or rough surfaced, disposed crosswise of thepath through which the sheet material I4 is to travel through theapparatus, the rolls I5 and I6 being shown as backed by larger rolls I1and I8 for preventing deflection of the rolls I5 and I6 under the stressto which they are subjected in the sheet-bending operation hereinafterdescribed. The pair of rolls I5 and I1 and the pair of rolls I6 and I8are relatively adjustable toward and away from each. other in anysuitable way, to vary the spacing of the rolls I5 and I6 between which,when in open position as shown in Fig. 2, the sheet material I4 isforced by the operator into looped condition as shown at I9 in thisfigure.

The apparatus shown also comprises a stiff rod 20, as for example ofsteel, which the operator inserts endwise into the loop I9 of Fig. 2,this rod serving when the pairs of rolls l5 and I1, and I6 and I8 arerelatively adjusted toward each other into close relationship, as forexample as shown in Figs. 1 and 2, to prevent the loop I9 from becomingwithdrawn from between the rolls I5 and I6 and effect the bending ofsuccessive portions of the sheet material I4 at this point in the travelof the sheet material through the apparatus.

Adjacent, and above, the rolls I1 and I8 are rolls 2| and 22 over whichthe sheet material I4 passes in its travel through the apparatus, therolls 2| and 22 being provided to maintain the sheet material out ofcontact with the rolls I1 and I8.

As will be understood, the initial pull on the sheet material exerted bythe feed means therefor and which may be the skin mill itself, causesthe loop I9 to be drawn from the relatively greatly expanded conditionshown in Fig. 2, into the closely contracted position shown in Figs. 1and 3, thereby causing the sheet material to become taut about the rollsl5 and I6 and the rod 20. Thus as the sheet material feeds lengthwisebetween the rolls l5 and I6 and over the rod (the rolls and rod rotatingin this movement of the sheet material and the portions of the sheetmaterial above the rod 20 being out of contact with each other) thesheet material is caused to become transversely bent or deformed aboutthe rolls and rod, sharp bending occurring at successive portions of thesheet material as it travels over this rod. Thus each succeeding portionof the sheet material M in passing around the rod is caused to be bentsharply transversely thereof in one direction and is restored to itssubstantially straight condition (but flatter than it was when itentered the bending means l3) in moving beyond the sheet-bending means,it having been demonstrated in practice that by subjecting the sheetmaterial to such bending action it becomes stretched resulting in thehardening or tempering thereof. Any tendency of the rod 20 to travellengthwise during the travel of the sheet material through the apparatusmay be overcome by any suitable means as for example by providing spacedapart posts 20a oposing the ends of the rod.

As a specific example of procedure and proportions of parts of theapparatus within my invention the following may be cited, but withoutany intention of limiting the invention thereto:

Hot rolled strip material, such as for example steel of the compositioncommonly used in the making of tin-plate, from which the finished sheetsare to be produced, as for example to be plated with molten tin or terneto produce plated sheets, is cold reduced from the hot, band size atleast about50% on a tandem mill in accordance with common practice, toabout gage or lighter, as desired, the sheet material in this operationbeing rolled into relatively long, wide strip-sheet form. The materialthus rolled is' wound into a coil, then cleansed in uncoiled condition,in accordance with common practice,

and then again coiled and in coil form subjected to an annealingoperation, preferably thorough,

as will be understood by those skilled in the art and in accordance withthe common practice of making tin-plate, namely, subjected to such heatand for such length of time as to cause all portions of the sheetmaterial to become completely annealed and render the material ofmaximum softness throughout. The annealed material is then passed inuncoiled, but in strip sheet condition, through the apparatus shown inFigs. 1-4 and above described, to cause it to become hardened andflattened, in such operation becoming somewhat reduced in thickness byelongation, receiving its slight final hardening by a slight reductionin the smooth roll skin mill, the hardening or tempering of the sheetthus produced being of such degree as to insure the retention in thefinished metal coated sheet material after subjection to the temperatureused in the applying of the metal coating, of suflicient temper to avoidfluting or stretcher strains as above referred to.

The sheet material is then cut into the desired sheet lengths; pickledas by sulfuric acid in accordance with common practice; and then coatedwith the desired metal, as for example, molten tin, to form tin-plate,in accordance with common practice.

As an example of the proportioning of the or temper as in the case oftin-plate as most commonly provided and requiring about a 5% reductionof the sheet material after annealing, in which case the sheet materialwould be rolled to about .0107 inch thickness in the cold mill, therolls l5 and I6 may be about 5 inches in diameter and the rod 20 aboutinch in diameter.

Sheet materialsubjected to the procedure and with the apparatus as abovedescribed (employing the rod 20 of about inch diameter) is stressed bythe action of the sheet-bending means to the point of developingminutely spaced minute substantially parallel surface fracturesextending transversely of the sheet material, these fractures because oftheir mlnuteness being almost imperceptible and so minutely spaced apartthat in the bending of the finished sheet material to shape, as forexample to form can bodies, any deviation from true circular form of theshaped body, is imperceptible. I

In those cases where it is desired that the sheet I material be hardenedor tempered to a less degree than in the specific example above given,the rod 20 would be. provided-of a larger diameter than about A; inchdepending on the degree of hardness or temper desired to be produced inthe sheet material, the larger the diameter of the rod 20 the less theelongation of the sheet material and thus the less resultant hardness ortemper in the sheet material and the greater the spacing of thefractures produced in the sheetbending operation. Experiments show thatsheet material. in which the fractures are spaced apart more thanpresent a. degree of hardness insufiicient to be of practical utility.

While apparatus of the construction above described has been found tooperate very satis factorily for the hardening and flattening of ferroussheet material and is preferred to be used for this purpose, theinvention is not limited thereto as the hardening and flattening of thesheet material employing the sheet-bending principle resulting insurface fracturing the sheet material, may be effected by the use ofother apparatus, such as for example that shown in Fig. 5.

The apparatus in accordance with Fig. 5 operates to bend successiveportions of the sheet material transversely thereof by pulling the sheetmaterial across a stationary straight edge which causes the sheetmaterial to sharply bend at such straight edge at successive portions ofthe material as it is pulled across the straight edge.

This apparatus in the form shown comprises a stationary straight edge 23beyond and below which is a roll 24 and beyond this roll a skin mill 25which may be of the same construction as the skin mill I0.

The sheet material M to be operated on and which may be supplied in coilform to the apparatus, is threaded over the straight edge 23 and underthe roll 24 and through the work rolls of the skin mill 25. I

The straight edge 23, the coil of sheet material l4 and the roll 24 areso relatively disposed as shown that in pulling the sheet materialthroughthe apparatus successive portions thereof are caused to betransversely sharply bent at the straight edges 23, resulting in thehardening and flattening of the sheet material in being dragged acrossthis straight edge; the sheet material being so stressed in thesheetbending operation referred to as to produce minute substantiallyparallel transverse fractures spaced apart.

The degree of hardness or temper and the closeness of spacing of theminute fractures produced in the sheet material depends on the degree towhich the portions of the sheet material at opposite sides of thestraight edge 23 diverge; any suitable means being provided for varyingthis degree as desired, as for example by adjust ably mounting the roll24 for adjustable setting further from, or closer to, the straight edge23, the less the divergence between said portions of the sheet material,the harder the resultant sheet material and the closer the fractures toeach other even to the degree of being minutely spaced apart.

The use of a skin mill in the structures shown gives to the finishedsheet material the desired surface appearance, as for example in thecases of black plate and tin-plate orterne, either a smooth or dullfinish, as desired, in the latter case the work rolls of the skin millbeing rough surfaced.

As will be understood, the gage to which the sheet material should berolled for subjection to the sheet-bending operation in producing afinished sheet of the desired gage, will depend on the degree to whichthe sheet material is elongated in the sheet-bending operation, thisbeing dependent on the diameter of the rod 20, in the case of theaparatus of Figs. 1-4 and the angle of divergence of the portions of thesheet material at opposite sides of the straight edge 23 in the case ofthe apparatus of Fig. 5, and also the degree of elongation produced bythe skin mill when used, and thus the sheet material should be rolled toa gage substantially equal to the gage desired of the finished sheetmaterial plus the amount of reduction produced by the sheet-bendingoperation when not followed by a skin rolling operation, or the sum ofthe reductions produced by the sheet bending operation and the skinrolling operation when the sheet-bending operation is followed by a skinrolling operation.

Furthermore, it Will be understood that, inasmuch as the skin rollingoperation, when employed, produces elongation of the sheet material, thedegree of such elongation should be taken into account in determiningthe sum total of the elongation to be produced in the sheet material forproducing the desired degree of hardness of the sheet material, and theroll 20 be provided of such diameter in the case of the aparatus shownin Figs. 1-4, or the portions of the sheet material at opposite sides ofthe straight edge 23 in the case of the apparatus shown in Fig. 5 berendered divergent at such an angle, that the elongation produced in thesheet-bending operation plus the elongation produced by the skin rollingoperation will equal the total amount of the elongation of the sheetmaterial desired to be produced.

The character of surface imparted to the sheet material by asheet-bending operation within my invention, whereby the sheet materialis fractured as described, renders the sheet material particularlyadapted, when the skin rolling operation is omitted, to its use in manysituations where such a surface is desirable as for example Where it isdesired that the sheet material be painted or lacquered, lithographed orlead-coated.

While I have illustrated and described certain particular constructionsof apparatus embodying my invention and have described my improvedmethod as practiced by certain forms of apparatus, I do not wish to beunderstood as intending to limit my invention thereto as the apparatusesshown may be variously modified and altered and provided in other forms,and my novel method variously modified and altered and practiced byvarious modifications and alterations of the apparatuses illustrated anddescribed and by other forms of apparatus, without departing from thespirit of my invention.

What I claim as new,and desire to secure by Letters Patent, is: v

1. The method of hardening ferrous sheet material which comprisesbending successive portions of thesheet material transverselysufliciently to so stress the sheet material as to surface-fracture it.

2. The method of hardening ferrous sheet material which comprisessharply bending successive portions of the sheet material transverselysufficiently to so stress the sheet material as to surface-fracture it.

3. The method of hardening ferrous sheet material which comprisesbending success ve portions of the sheet material transverselysufficiently to so stress the sheet material as to surface-fracture itand thereafter skin rolling the sheet material. I

4. The method of hardening ferrous sheet material which comprisesbending successive portions of the sheet material transverselysufliciently to produce minute transverse surface fractures in the sheetmaterial.

5. The method of hardening ferrous sheet material which comprisesbending successive portions of the sheet material transverselysufficiently to produceminutely spaced minute transverse surfacefractures in the sheet material.

6. The method of hardening ferrous sheet material which comprisesbending successive portions of the sheet material transverselysufficiently to produce minute transverse surface fractures in the sheetmaterial and thereafter skin rolling the sheet material.

7. The method of hardening ferrous sheetmaterial which comprises loopingthe material between spaced apart members, lengthwise feeding the sheetmaterial between the members and maintaining the sheet in loopedcondition between the members while permitting travel of the sheetmaterial, the looping being sufficient to cause the sheet material inits travel to be so stressed transversely as to surface fracture it 8.The method of hardening ferrous sheet material which comprises draggingthe sheet material over a straight edge in such direction relative tothe plane of the sheet material as to produce a succession of suchrelatively sharp transverse deflections of the sheet material at saidstraight edges as to produce surface fracturing of the sheet material.

9. An apparatus for hardening ferrous sheet material comprising spacedapart members between which the sheet material is transversely looped, asheet-bending element disposed within the loop in the sheet material andrestrainthe withdrawal of the loop from between said members, means forpulling the sheet material lengthwise in engagement with said membersand element, said sheet-bending element being of such cross-sectionalarea as to cause the sheet material in its travel to be so stressedtransversely as to surface fracture it, and a skin millfor skin rollingthe sheet material.

11. An apparatus for hardening ferrous sheet material comprising spacedapart rolls between which the sheet material is transversely looped, asheet-bending element disposed within the loop in the sheet material andrestraining the withdrawal of the loop from between said members, andmeans for pulling the sheet material lengthwise in engagement with saidmembers and element, said sheet-bending element being of such crosssectional area as to cause the sheet material in its travel to be sostressed transversely as to surface fracture it.

12. An apparatus for hardening ferrous sheet material comprising spacedapart members between which the sheet material is transversely looped, arod disposed within the loop in the sheet material and restraining thewithdrawal of the loop from between said members, and means for pullingthe strip material lengthwise in engagement withsaid membersandrod.

13. An apparatus for hardening ferrous sheet material comprising meansfor feeding the sheet material, and means for bending the sheet materialtransversely at successive portions thereof in the feeding of the sheetmaterial sufficiently to surface-fracture the sheet material.

14. An apparatus for hardening ferrous sheet material comprising astraight edge for engagement with sheet material fed across it, andmeans for pulling the sheet material across said straight edge in adirection to produce deflection of successive portions of the sheetmaterial at said straight edge sufiiciently to surface-fracture thesheet material. I p

15. An apparatus for hardening ferrous sheet material comprising astraight edge for engages ment with sheet material fed across it, meansfor pulling thesheet material across said straight edge in a directionto produce deflection of successive portions of the sheet material atsaid straight edge suiiiciently to surface-fracture the sheet material,and a skin mill for skin rolling the sheet material.

, 16. Ferrous sheet material which is the product of the method of claim1.

1'7. Ferrous sheet material which is the product of the method "of claim6. r

18. Hardened ferrous sheet material having substantially parallelsurface .fractures spaced apart substantially uniformly overthe surface.

19. Hardened ferrous sheet material having substantially parallelsurface fractures closely spaced apart substantially uniformly over thesurface.

20. An apparatus for hardening ferrous sheet material comprising spacedapart members between which the sheet material is transversely looped, asheet-bending roller element disposed within the loop in thesheet-material and restraining the withdrawal of the loop from betweensaid members, and means forpulling the sheet material lengthwise inengagement with said members and element, said sheet-bending elementbeing of such cross sectional area as to cause the sheet material in itstravel to be so stressed transversely as .to surface fracture it.

21. An apparatus for hardening ferrous sheet material comprisingspacedapart rolls between which the sheet material is transverselylooped, a sheet-bending roller element disposed within the loop in thesheet material and restraining the withdrawal of the loop from betweensaid members, and means for pulling the sheet material lengthwise inengagement with said members and element, said sheet-bending elementbeing of such cross sectional area as to cause the sheet material in itstravel to be so stressed transversely as to surface fracture it.

WILLIAM J. WALSH.

